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do the wattmeters differ between the power genius and the tuner genius??

the amp reads about close to 100 watts more than the tuner?? also does anybody also get a red low power reading sometimes on the tuner do you have to bypass the tuner on the 6600 or the software will take of that tnx


  • Mike-VA3MW
    Mike-VA3MW Administrator, FlexRadio Employee, Community Manager, Super Elmer, Moderator admin

    There are a few reasons.

    Sometimes it depends on the accuracy of the watt meters. If you really want to compare them, make sure you test on a 50 ohm dummy load with a perfect SWR.

    More of it is explained here: https://www.arrl.org/files/file/Technology/tis/info/pdf/q1106037.pdf

  • Hal Massey
    Hal Massey Member ✭✭

    I feel compelled to help out by providing a more general answer that can be used well beyond the Flex, PGXL, and TGXL world. This answer can be used anywhere to help understand making a measurement like this.

    A well known expensive lab grade wattmeter made by Bird can be used to illustrate the Physics that applies here to all rigs and all radio, tuner, and wattmeter tuples.

    With the 2000 Watt HF range selected on this well known lab grade wattmeter used by hams for decades the error is stated in the user manual as (+/- 5% full deflection).

    If we could create an imaginary signal of precisely 2,000.000 Watts that high quality lab grade wattmeter could read anywhere from 1900 to 2100 Watts and everything would be perfectly normal.

    Or said in economic terms. You have to spend more and more money if you want to get more and more accurate absolute measurements (as opposed to relative ones).

    This example relied on a purpose built lab grade wattmeter.

    The wattmeters in ham gear are convenient add ons that are not purpose built. The rigs were purpose built to make QSO's not to measure watts.

    Having said that I have been pleasantly surprised by how good the Flex wattmeters are when all things considered

    Hope that helps.


    -Hal Massey / WB6NNR

  • Mike VE3CKO
    Mike VE3CKO Member ✭✭✭

    Great explanation Hal, this use be cut and pasted to all future responses to "Why are my readings different?"

  • Alan
    Alan Member ✭✭✭✭

    I grew up in the analog measurement world.

    Measurement uncertainty has been lost on today's digital users.

    For example. What is the average of two measurements expressed as; 3 and 4?

    Did you answer 3.5? No, it's not. You "invented" an additional significant digit.

    The correct response is, the average is greater than 3 and less than 4,

    If I asked, what is the average of 3.0 and 4.0, assuming the measurement device is accurate to the nearest 1/10 unit, the correct answer is, 3.5.

    Another lesson, when in doubt, always use three measurement devices of equal precision and range, all measuring the same paramater. 

    Alan. WA9WUD

  • KD0RC
    KD0RC Member, Super Elmer Moderator

    Segal's Law... A man with a watch knows what time it is. A man with two watches is never sure.

  • Bill AB7AA
    Bill AB7AA Member ✭✭✭

    This is my watt meter comparison, obviously into a dummy load. On SSB it is continuously a 2:1 ratio. So which one is correct? Do I conservatively operate below 1500 watts on the highest meter and perhaps only paid for a 750 watt amp? It's been 20 days since Flex support last communicated with me.


    Bill AB7AA

  • WX7Y
    WX7Y Member ✭✭✭
    edited February 2022

    The Amp INPUT is only 1456 Watts (P=I of 28A x E of 52V = P of 1456 Watts input) so unless the AMP is running at 195% efficiency it CAN'T be 1949 Watts. Remember the P=IE formula?

    My Tuner Genius has a pretty accurate Meter compared to other high accuracy Watt meters, and I would believe hands down the Tuner Genius Metering.

  • Mike-VA3MW
    Mike-VA3MW Administrator, FlexRadio Employee, Community Manager, Super Elmer, Moderator admin

    @Bill AB7AA

    That looks like you are in SSB mode when you did the screen capture.

    What does it look like with just a carrier?


  • Bill AB7AA
    Bill AB7AA Member ✭✭✭


    With just a carrier it is only about 250 watts different. That is the info I sent to support, which is much better. But when you're running SSB, what you see above is all that you can adjust from. If I adjust the drive level with carrier only, then on SSB you get the above.

    In fairness to Flex support, Dan said that his software engineer was going to be gone 10 days. Even at that, he should have been back for about a week.


    I don't know the PGXL sample interval among P, E, I and therefore may not yield a simple P=IE calculation.


  • Mike-VA3MW
    Mike-VA3MW Administrator, FlexRadio Employee, Community Manager, Super Elmer, Moderator admin


    Calculating Peak Envelope Power is complicated. It requires significant sampling to come up with the Peak power in the envelope. The algorithms in the amplifier are different than in the TGXL. Our software developer who works on the PGXL has spent significant hours working on it. But, as Dan said, he is on vacation.

    It is a work in progress. For me, the only watt meter I own that is a 'Bench Standard Calibration' is my LP-100A. The rest are informational only and are good enough to tell me if I am getting lots of watts or minimal watts.

    tldr; both are working as designed.

  • With PGXL 3.6.24 installed...

    On 17M, with the 6600M on tune, connected to a Palstar DL2K dummy load

    PGXL 331 W

    LP-500 331 W

    Palstar HF- Auto set to bypass 300 W

    Dummy load analog meter about 297 W

    Occasionally the PGXL meter jumps between 330W to 354W, while all other meter readings are rock solid.

    Close enough for amateur radio work?

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